1. Field of the Invention
The present invention relates to a fluid pressure control device for use, for example, in the braking system of a vehicle, and comprising a housing which has an input port connected to a fluid pressure supply source, an output port leading to a fluid pressure operated device and a release port connected to a reservoir; a sliding member slidably fitted in the housing between a retracted position connecting the output port with the release port and an advanced position connecting the output port with the input port; a reaction chamber in the housing and facing a front surface of the sliding member for generating a fluid pressure urging the sliding member in a retracting direction, the reaction chamber being connected to the output port; an urging piston slidably fitted in the housing and operatively connected to a rear end of the sliding member; an input piston slidably fitted in the housing and operatively connected to an operation member; and a pressure chamber formed between a back surface of the urging piston and a front surface of the input piston.
2. Description of the Prior Art
Such a fluid pressure control device is conventionally known, for example, from Japanese Patent Application Laid-open No. 220054/91.
In the above prior art fluid pressure control device, pressure receiving areas of the urging piston and the input piston, each exposed to the pressure chamber, are set at an equal value. Hence, if the fluid pressure is varied in a condition in which there is such fluid pressure generated in the reaction chamber, the variation in pressure in the pressure chamber, due to the forward and rearward sliding movement of the sliding member, is relatively large, resulting in a relatively large kick-back applied from the input piston to the operation member. In addition, when the operation member is further operated from a condition in which the sliding member cuts off the communication between the output port and the input port, thereby advancing the sliding member, the ratio of the amount of input piston advanced to the amount of urging piston advanced is 1:1. Therefore, a force required to advance the sliding member to a position in which the output port and the input port are put into communication with each other is relatively large.